Net I=B=R Capacity (BTU)
I=B=R, also referred to as Net Output or AHRI Capacity, is the rated heat output of a boiler after accounting for combustion efficiency, piping loss, and an extra pickup factor. We recommend sizing steam boilers based on the I=B=R rating.

To

30000 - 169999 (161)

170000 - 309999 (36)

310000 - 449999 (6)

450000 - 589999 (4)

590000 - 729999 (3)

730000 - 869999 (6)

870000 - 1009999 (3)

1010000 - 1149999 (3)

1150000 - 1289999 (5)

1290000 - 1429999 (3)

1430000 - 1569999 (4)

1570000 - 1709999 (4)

1710000 - 1849999 (4)

1850000 - 1989999 (1)

DOE Heating Capacity (BTU)
Also referred to as Gross Output, this is the output of a boiler after accounting for combustion efficiency. We recommend sizing hot water boilers based on the DOE Heating Capacity.

Maximum Input Capacity (BTU)
The Maximum Input Capacity describes how quickly the appliance will use fuel when delivering it's maximum capacity. The units may change depending on the fuel being used.

50000 - 239999 (150)

240000 - 429999 (25)

430000 - 619999 (6)

620000 - 809999 (4)

810000 - 999999 (2)

1000000 - 1189999 (6)

1190000 - 1379999 (2)

1380000 - 1569999 (6)

1570000 - 1759999 (2)

1760000 - 1949999 (2)

1950000 - 2139999 (6)

2140000 - 2329999 (2)

2330000 - 2519999 (4)

2520000 - 2709999 (2)

AFUE (%)
AFUE (Annual Fuel Utilization Efficiency) measures the efficiency of combustion equipment over the entire heating season, and is calculated by dividing the amount of energy that is actually heating your home by the total energy contained in the fuel used by the boiler/furnace. Learn More

Vent Type
Products that use combustion (burning) of fuel to create heat also create potentially dangerous gasses that need to be exhausted (AKA "Vented"). Depending on the product, venting can be done via a chimney, through a side wall, or use a second vent to provide fresh air to the appliance.

Chimney Vent (200)

Direct Vent (44)

Power Vent (61)

Medium
Medium refers to the substance that carries heat through the heating system. Systems are either designed to use either Hot Water or Steam as a medium, and components are usually specific to one or the other.

Hot Water (210)

Hot Water/Steam (9)

Steam (66)

Fuel Type
To create heat, some form of fuel is required. Fuel Type specifies what the product uses as an input to create heat.

Indirect Fired (10)

Liquid Propane (77)

Natural Gas (251)

Oil (65)

Modulating/Staging
Stages are unique speeds or levels that equipment can operate at. More stages allow for better fine-tuned control of output, which improves comfort and efficiency. Modulating equipment can operate across a range of levels, giving the highest level of fine-tuned control. Learn More

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